SystemsofEquations(2)

　　2　(2x + 3y = –6) = 4x + 6y = –12

　　Now add the equations and solve for y.　　When you solve for one variable, like we have in this last example, you can solve for the second variable using either of the original equations. If the last question had asked you to calculate the value of xy, for example, you could solve for y, as above, and then solve for x by substitution into either equation. Once you know the independent values of x and y, you can multiply them together.　　Simultaneous equations on the Math IC will all be this simple. They will have solutions that can be found easily by adding or subtracting the equations given. Only as a last resort should you solve for one variable in terms of the other and then plug that value into the other equation to solve for the second variable.

（责任编辑：申月月）